PHYS 445 Supplement  Quick and dirty quantum mechanics
S  1
© 2001 by David Boal, Simon Fraser University.
All rights reserved; further resale or copying is strictly prohibited.
Supplement  Quick and dirty quantum mechanics for PHYS 445
What's Important:
•
old quantum theory
•
particle in a 1D box
•
rigid rotor
•
harmonic oscillator
Old quantum theory
A very simple approach to quantization is based upon interference, where the wave in
question comes from de Broglie. In systems with repetitive motion, the idea is to
demand that the motion contain an appropriate number of de Broglie wavelengths to
form a constructive standing wave.
The de Broglie wavelength, as we recall is
=
h
/
p
where
= de Broglie wavelength
h
= Planck's constant
p
= particle momentum.
We reason by example.
1.
Particle in a 1dimensional box
Here, the motion is in one dimension between two perfectly reflective walls.
Since
there is no potential energy gradient in the region between the walls, the particle's
energy and momentum must be constant.
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 Spring '08
 DavidBoal
 Physics, mechanics, Energy, David Boal, dirty quantum mechanics

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